Schrauf wrote:
They wanted the 10 AM slot for the east coast time zone, but that would be 7 AM in Phoenix, which would be ideal when the projected high would be in the high 80's or warmer that time of year. Phoenix is mountain time zone but does not recognize DST. You would never hold a race there in March for a "fast race" but to select the best team for LA it would work okay.
The bid book for the '28 Trials states "The broadcast window for this event will be from 12:00 pm to 3:00 pm EST on either March 25, 2028 or March 26, 2028." (It also states, of course, that this "is subject to change, at USATF's sole discretion," so I guess it technically could be changed to fit the weather of the bid... but this was probably set by NBC, and what NBC wants, NBC usually gets from USATF.) See p. 5 of this doc for the citation: https://www.usatf.org/USATF/media/USATF/PDFS/2028-U-S-Olympic-Team-Trials-Marathon-RFP_2.pdf
With Phoenix being in the Mountain time zone but not observing daylight savings time and St. Louis being in the Central (and doing all the normal clock-change stuff) that would put the broadcast as starting at 9am local time in Phoenix and 11am in St. Louis, with the races likely starting just a few minutes after that in either location.